1. Field of the Invention
This invention relates generally to a surgical instrument useful in injecting thermal and/or radioactive seeds percutaneously into a body organ, and more particularly to an instrument of the type described which is effective to deposit such seeds in a desired axial alignment.
2. Discussion of the Prior Art
In the Paulus et al. U.S. Pat. No. 5,429,583, there is described a seed of a ferromagnetic material which when injected into body tissue and subsequently exposed to an oscillating magnetic field produces localized heating of the tissue surrounding the seed for therapeutic purposes. For example, if the seeds are injected into the prostate gland, the heating may be used to shrink the prostate gland in addressing BPH. Radioactive seeds have also been injected into tumorous tissue so that the resulting radiation given off by the seeds will destroy the cancerous tissue.
Pending application Ser. No. 08/864,486, filed May 28, 1997, describes a method for manufacturing a combination ferromagnetic/radioactive seed whereby both radioactive emissions and heat can simultaneously be applied to selected tissue structures.
When it is considered that to achieve optimum magnetic coupling between implanted ferromagnetic seeds and an external magnetic field producing coil, there must be appropriate alignment of the applied field to the implanted seeds, an instrument is required that can be used to inject such seeds so as to be aligned along a desired axis so that the patient's body can be appropriately oriented with respect to the external field coil.
The Scott U.S. Pat. Nos. 4,402,308 and 5,242,373 describe medical instruments for percutaneously injecting radioactive seeds into tumorous tissue. Generally, they comprise a tubular hypodermic needle into which radioactive seeds may be fed. A push rod is provided for effectively forcing the seeds out of the distal end of the tubular needle. However, the device tends to be difficult to manipulate and often results in misaligned seeds following their implantation.
Thus, a need exists for an instrument that allows precise deposition of thermal/radioactive seeds into body tissue with the seeds being aligned with a predetermined axis.